Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA damage induced by visible light in L1210 mouse leukaemia cells was analysed by an alkaline elution assay with specific repair endonucleases. DNA single-strand breaks and DNA modifications sensitive to FPG protein (formamidopyrimidine-DNA glycosylase), endonuclease III and exonuclease III were quantified in parallel. The light-induced cellular DNA damage was found to consist of many base modifications sensitive to FPG protein, which most probably are predominantly 7,8-dihydro-8-oxoguanine (8-hydroxyguanine) residues. Base modifications sensitive to endonuclease III are virtually absent. The yield of the FPG-sensitive base modifications is 10-fold higher than that of single-strand breaks plus AP sites (sites of base loss). The described ratios of the various modifications indicate that the damage most probably results from a reaction of DNA with singlet oxygen (type II reaction) or directly with an excited endogenous photosensitizer (type I reaction) and is not mediated by hydroxyl radicals. Experiments with cut-off filters indicate that wavelengths between 400 and 500 nm are responsible for most of the modifications. The FPG-sensitive base modifications are repaired efficiently (t1/2 approximately 1 h at 37 degrees C). This is perhaps why the light-induced DNA damage is apparently associated with only low mutagenicity.
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PMID:Visible light generates oxidative DNA base modifications in high excess of strand breaks in mammalian cells. 831 21

Chemotherapeutic agents used in the treatment of cancer often lead to dose-limiting bone marrow suppression and may initiate secondary leukemia. N,N',N"-triethylenethiophosphoramide (thiotepa), a polyfunctional alkylating agent, is used in the treatment of breast, ovarian, and bladder carcinomas and is also being tested for efficacy in the treatment of central nervous system tumors. Thiotepa produces ring-opened bases such as formamidopyrimidine and 7-methyl-formamidopyrimidine, which can be recognized and repaired by the formamidopyrimidine glycosylase/AP lyase (Fpg) enzyme of Escherichia coli. Using this background information, we have created constructs using the E. coli fpg gene along with the functional equivalent human ortholog alpha-hOgg1. Although protection with the Fpg protein has been previously observed in Chinese hamster ovary cells, we demonstrate significant (100-fold) protection against thiotepa using the E. coli Fpg or the human alpha-hOgg1 cDNA in NIH3T3 cells. We have also observed a 10-fold protection by both the Fpg and alpha-hOgg1 transgenes against 1,3-N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) and, to a lesser extent, mafosfamide (2-fold), an active form of the clinical agent cyclophosphamide. These latter two findings are novel and are particularly significant since the added protection was in an O(6)-methylguanine-DNA methyltransferase-positive background. These results support our general approach of using DNA base excision repair genes in gene therapy for cellular protection of normal cells during chemotherapy, particularly against the severe myelosuppressive effect of agents such as thiotepa, BCNU, and cyclophosphamide.
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PMID:Protection of mammalian cells against chemotherapeutic agents thiotepa, 1,3-N,N'-bis(2-chloroethyl)-N-nitrosourea, and mafosfamide using the DNA base excision repair genes Fpg and alpha-hOgg1: implications for protective gene therapy applications. 1118 13

Potassium bromate (KBrO3), a food additive, induces renal-cell tumors in rats. KBrO3 induced 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) formation in human leukemia cell line HL-60 as well as in its H2O2-resistant clone, HP100, suggesting no involvement of H2O2. Depletion of GSH by buthionine sulfoximine (BSO) had a little inhibitory effect on KBrO3-induced 8-oxodG formation. However, the amount of 8-oxodG was still significantly higher than that in control, suggesting that intracellular Cys can affect KBrO3 to oxidize DNA, when GSH decreased. KBrO3 caused 8-oxodG in isolated DNA in the presence of GSH (tripeptide; gamma-GluCysGly), gamma-GluCys, CysGly, or Cys. Methional completely inhibited 8-oxodG formation induced by KBrO3 plus GSH, but typical hydroxyl radical scavengers, SOD and catalase, had little or no inhibitory effects. When bromine solution (BrO(-)) was used instead of BrO3(-), similar scavenger effects were observed. Experiments with 32P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene suggested that KBrO3 induced 8-oxodG formation at 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of GSH and that treatment of formamidopyrimidine-DNA glycosylase led to chain cleavages at the guanine residues. ESR spin-trapping studies showed that 1:2:2:1 quartet DMPO (5,5-dimethyl-1-pyrroline N-oxide) spectrum similar to DMPO/hydroxy radical (*OH) adduct, but the signals were not inhibited by ethanol. Therefore, the signal seemed not to be due to *OH but byproduct due to oxidation of DMPO by the reactive species. The signals were suppressed by the addition of dGMP, but not by other mononucleotides, suggesting the specific reactivity with guanine. On the basis of our results and previous literature, it is speculated that reduction of KBrO3 by SH compounds in renal proximal tubular cells yields bromine oxides and bromine radicals, which are the reactive species that cause guanine oxidation, leading to renal carcinogenesis of KBrO3.
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PMID:Requirement of glutathione and cysteine in guanine-specific oxidation of DNA by carcinogenic potassium bromate. 1140 38

Doxorubicin (DOX) is an effective anthracycline antibiotic against a wide spectrum of tumors and hematological malignancies. It mainly interacts with DNA, but can also generate reactive oxygen species (ROS), which damage cell components. Unfortunately, numerous side effects, such as severe cardiotoxicity and bone-marrow suppression, limit its use. To reduce this obstacle and improve its pharmacokinetics, we conjugated DOX to transferrin (TRF), a human plasma protein. In our study, we compared the effect of DOX and the doxorubicin-transferrin conjugate (DOX-TRF) on human leukemic lymphoblasts (CCRF-CEM), and on normal peripheral blood mononuclear cells (PBMC). In parallel, experiments were carried out on two human chronic myeloid leukemia (CML) cell lines derived from K562 cells, of which one was sensitive and the other resistant to doxorubicin (K562/DOX). By use of the alkaline comet assay, the effect of the agents on the induction of DNA damage in normal human cells and human leukemia cells was determined. Oxidative and alkylating DNA damage were assayed by a slightly modified comet assay that included the use of the DNA-repair enzymes endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg). To investigate whether DNA breaks are the result of apoptosis, we examined the induction of DNA fragmentation visualized as oligosomal ladders after simple agarose electrophoresis under neutral conditions. Modifications of the genome induced by the different drugs were analyzed following assessment of the cell-cycle phase. The DOX-TRF conjugate caused more DNA damage than the free drug, the degree of DNA fragmentation being dependent on the duration of treatment and the cell type analyzed. With neutral agarose electrophoresis we showed that the test compounds caused the formation of a characteristic DNA-ladder pattern. Furthermore, the DOX-TRF conjugate generated a higher percentage of apoptotic cells in the subG1 fraction and blocked more cells in the G2/M phase of the cell cycle than did free DOX. In summary, both agents induced DNA damage in cancer cells, but the DOX-TRF conjugate generated more genotoxic effects and apoptosis than the unconjugated drug.
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PMID:Genotoxic effect of doxorubicin-transferrin conjugate on human leukemia cells. 2530 42

Chloramphenicol (CAP) was an old antimicrobial agent. However, the use of CAP is limited because of its harmful side effects, such as leukemia. The molecular mechanism through which CAP has been strongly correlated with leukemogenesis is still unclear. To elucidate the mechanism of genotoxicity, we examined DNA damage by CAP and its metabolites, nitroso-CAP (CAP-NO), N-hydroxy-CAP (CAP-NHOH), using isolated DNA. CAP-NHOH have the ability of DNA damage including 8-oxo-7,8-dihydro-2'-deoxyguanosine formation in the presence of Cu(II), which was greatly enhanced by the addition of an endogenous reductant NADH. CAP-NO caused DNA damage in the presence of Cu(II), only when reduced by NADH. NADH can non-enzymatically reduce the nitroso form to hydronitroxide radicals, resulting in enhanced generation of reactive oxygen species followed by DNA damage through the redox cycle. Furthermore, we also studied the site specificity of base lesions in DNA treated with piperidine or formamidopyrimidine-DNA glycosylase, using (32)P-5'-end-labeled DNA fragments obtained from the human tumor suppressor gene. CAP metabolites preferentially caused double base lesion, the G and C of the ACG sequence complementary to codon 273 of the p53 gene, in the presence of NADH and Cu(II). Therefore, we conclude that oxidative double base lesion may play a role in carcinogenicity of CAP.
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PMID:Oxidative DNA damage induced by metabolites of chloramphenicol, an antibiotic drug. 2597 46